1. Field of the Invention
The present invention relates to a modified powder or particulate material having a silicone polymer film coated on substantially the entire surface thereof. More specifically, it relates to a modified powder or particulate material obtained by treating a powder or particulate material having active sites on the surface thereof with a certain silicone compound in the form of a vapor, whereby the surface activities of the powder or particulate material are made to disappear. The term "powder or particulate material" (i.e., "powder material" hereinbelow) used herein means any material generally having a particle size of 10 mm or less, but sometimes more than 10 mm. The agglomerates and the molded or shaped products of the powder are also included in this term. The term "active site" used herein means those capable of catalytically polymerizing a silicone compound having a siloxane bond (Si--O--Si) or a hydrosilyl group (Si--H) (i.e., acidic, basic, oxidative, or reductive sites).
The modified powder material according to the present invention does not denature or decompose perfumes, oils, or resins even when coexisting therewith, and therefore, will not cause problems such as denaturation, odor change, and color change and can be utilized in the fields of, for example, cosmetics, pharmaceuticals, coating materials, inks, paints, decoratives, fragrants, magnetic materials, and medical materials.
2. Description of the Related Art
Silicone oils have been frequently used in the prior art for the hydrophobic modification of a powder material. For example, Japanese Examined Patent Publication (Kokoku) No. 41-9890 discloses imparting lubricity to an animal, vegetable or mineral powder by coating the surface of the powder with a silicone resin coating material, followed by drying and baking. In Japanese Examined Patent Publication (Kokoku) No. 45-2915, a mineral powder such as talc is simply attached with a silicone having hydrogen directly bonded to silicone in the molecular chain by, for example, blender mixing, followed by heating baking, thereby imparting a water repellency to the powder. According to Japanese Examined Patent Publication (Kokoku) No. 45-18999, talc is attached with dimethylpolysiloxane or methylhydrogenpolysiloxane by contact with an organic solvent solution thereof, followed by baking optionally with the addition of a substance such as zinc octoate as the cross linking polymerization catalyst for methylhydrogenpolysiloxane, thereby imparting a free flow property to the powder. Further, in Japanese Examined Patent Publication (Kokoku) No. 49-1769, titanium dioxide is subjected to direct coating, emulsion coating or solvent solution coating of various alkylpolysiloxanes, and then dried and baked optionally by using, in combination, an ester compound having a total carbon number of 6 or more, whereby the dust property, dispersibility, etc., of the powder are modified. On the other hand, in Japanese Unexamined Patent Publications (Kokai) Nos. 56-16404, 55-136213 and 56-29512, after mixing under stirring with the addition of silicone oils and oil agents or by the application of a mechanochemical reaction such as crushing, a baking treatment is performed.
Further, Japanese Unexamined Patent Publication (Kokai) No. 57-200306 discloses a method for imparting a water repellency and flow property to a powder without the application of a baking treatment by treating the powder with (A) a silane compound having a specific structure, (B) a cyclic polyorganosiloxane, and (C) a linear polyorganosiloxane. According to this method, 1 to 10% by weight based on the powder to be treated of the above organic silicone compound is adsorbed onto the powder by spraying a solution diluted in a solvent, direct spraying, or gaseous atomization, or by directly mixing under stirring, and then a water or water vapor treatment is applied. In the (B) cyclic polyorganosiloxane, the trimer having a methyl group is excluded, because it is solid and difficult to handle.
However, according to these methods, in most organic pigments and inorganic pigments, those weakly resistant to heat, such as yellow iron oxide or prussian blue, could not be treated.
For example, among the organic pigments, C.I. 15850:1 (lithol rubine BCA) could not be treated, because it was dehydrated at 80.degree. C. and changed crystal form from .alpha.-type to .beta.-type simultaneously with a change in tone. On the other hand, prussian blue is decomposed by the application of heat and gradually releases cyan gas at 150.degree. C. or higher. Baking treatment is carried out at 350.degree. C. for 2 hours, as a typical example of a higher temperature treatment, or at 150.degree. C. for 15 to 40 hours, as a typical example of a lower temperature treatment. Under such conditions, prussian blue not only undergoes a color change but also releases harmful cyan gas, thus being very dangerous.
Such a baking treatment of the prior art can be applied only for a part of stable inorganic pigments, and has the vital defect that treatment of an organic pigment which is brilliant among pigments impaired the tone of its color.
Indeed, treatment at a lower temperature is possible when a catalyst is used for lowering the baking temperature, but the catalyst remained, to promote deterioration of the silicone resin on the surface, and cause marked changes with a lapse of time. Thus, this method had little success in practical application, as a general rule. Also, the catalyst not only affects the silicone resin on the surface but also promotes decomposition of co-existing components such as oils or perfumes to cause the problems of denaturation or change of odor, etc., and therefore, it could not be used for cosmetics, etc.
Japanese Unexamined Patent Publication (Kokai) No. 56-16404 discloses a silicone treatment method utilizing a mechanochemical reaction. According to this method, because a crushing force is utilized, powder specifically shaped into plates or spheres suffers from a change in shape. Also, for a powder such as titanium dioxide, which will be agglomerated by stirring, even the treatment of it alone could be done only with difficulty.
In Japanese Unexamined Patent Publication (Kokai) No. 57-200306, in any case, the treating agent does not come into contact with the powder in the form of molecules but in the form of liquid or fine particles of liquid. For this reason, the trimer, which is solid, is excluded from cyclic polyorganosiloxanes. The amount of the treating agent is defined as 1 to 10% based on the powder, but such an amount may be insufficient depending on the kind of powder, whereby the surface activity of the powder remains and the stability of a perfume, if co-present, will be disadvantageously worsened.